The increasing popularity of bicycling in recent years has led to the profusion of bicycles equipped with variable speed transmissions that permit changing the gear ratio between the pedal sprocket powered and the drive sprocket of the rear wheel. A number of such gear shift arrangements are well known in the art and are commonly seen in ten-speed form and less frequently in five-speed or three-speed selectability.
Conventionally, the gears are shifted between the several ratios by means of manual selector levers operable through cables and mechanical linkage. More recently, there have been developed diverse means for effecting both automatic shifting of the gears without manual or hand operation of a lever, as well as fluid operated shifting devices, thereby to eliminate certain complexities of mechanical cable and linkage arrangements of the derailleur or other multi-speed bicycle gear changing assembly.
Developments of this type are seen illustratively in recent U.S. Pat. Nos. to Mathauser 3,742,777, Houghton 3,613,466, Dunder et al 3,873,128, Gardel 3,830,521 and Yamaguchi 3,732,787.